Question: $\dfrac{7}{8} - \dfrac{8}{10} = {?}$
Answer: $ = {\dfrac{7 \times 5}{8 \times 5}} - {\dfrac{8 \times 4}{10 \times 4}} $ $ = {\dfrac{35}{40}} - {\dfrac{32}{40}} $ $ = \dfrac{{35} - {32}}{40} $ $ = \dfrac{3}{40}$